Digital indicator circuitry



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Jan. 16, 1962 1 J. ANDREWS 3,017,102

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DIGITAL INDICATOR CIRCUITRY Jan; 16, 1962 l.. J. ANDREWS 3,017,102

DIGITAL INDICATOR CIRCUITRY Jan. 16, 1962 l.. J. ANDREWS 3,017,102

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c@ PZP, ed KES @Ww T@ States atet @hice annate Patented dan.. 16, it-62 we, Ca deviate; Company, Day on,

i1. in, i957. Ser. No. 634,524 i2 Ciairns. (Ci. ZES-476) This invention relates to circuitry for incrementally controlling the setting of an indicating device and, more particularly, to circuitry which provides voltage output pulses for incrementally repositioning a shaft to a rotational setting as defined by coded signals supplied by a digital computer, for example.

Control circuits for positioning devices employed to set a pointer, a shaft, the recording pen of a graph plotter, etc., corresponding to a binary coded signal, iind extensive utility in the fields of navigation, instrumentation, and others. Thus, in the field of navigation, in order to plot the relationship of a controlled vehicle to a reference vehicle, indicator means are used to show position, course, and speed. Each of these components may be represented by the angular displacement of a rotatable synchro-transmitter shaft to which an indicator pointer is coupled. The rotation of the shaft, in turn, could be employed to represent information utilized as a control for means operable to adjust, for instance, the steering mechanism of the vehicle.

lt is therefore an object of the present invention to provide relatively simple controlling means for supplying signals capable of altering the position of an electrically activated device in accordance with coded signals.

it is another object of this invention to provide logical circuitry having a high-speed programmed digital sequence for generating pulses defining the incremental actuation of a device from its present position toward a desired position.

it is another object of this invention to provide accomplishment of the aforementioned objects by a digital process utilizing the inhibit-wound magnetic core approach to logical circuitry mechanization as taught by a copending patent application Magnetic Core Logical Circuitry, Andrews et al., Serial No. 615,279, led October 1l, 1956.

A more complete understanding of this invention, as well as additional objects and features thereof, may be obtained by reference to the ensuing description of the drawings in which:

FIG. l is an overall block diagram of an embodiment of the invention.

FG. 2 is a flow diagram of the routine of the invention.

FIG. 3 is a schematic diagram of a typical register as utilized in the invention, being articularly the E register of the data processing unit.

FIG. 3a is the preferred hysteresis characteristic of the material of the magnetic cores utilized in the registers.

FIG. 3b is a group of timing current waveforms used for serially setting and interrogating the magnetic cores of the registers.

FIG. 4 is a block diagram of the E register transfer circuit.

FEG. 4a is a set of curves describing the operation of the E register transfer circuit.

PEG. 5 is a schematic diagram of the data processing unit, showing also input means and the output circuit.

FiG. 6 is a schematic diagram of the programming unit.

FIG. 6a is a graph illustrating the operation of the programming unit.

FIG. 7 is a schematic diagram of the F register of the data processing unit.

FIG. 8 is a schematic diagram of the A register o the data processing unit.

FiGS. 9, l0, and 1l are schematic diagrams of the l, K, and L registers, respectively, of the programming unit.

FIG. l2 is a schematic diagram of the output circuitry for the data processing unit utilized for driving the indicating device.

Generally, as shown in FG. l, the present invention, in the preferred embodiment, provides circuitry for generating pulse-type signals eifective to alter the rotational setting of the shaft of an indicating device t7, for example. Indicating device 17 includes a conventional pulse-actuated bi-directional stepping motor, such as is disclosed in an article entitled A Bi-Directional Pulse Totalizer for Control and Telemetry, by H. Dudley Wright, published in the Convention Record of the Institute of Radio Engineers, 1956. In accordance with the invention, signals representing, for instance, a desired bearing of a vehicle and consequently also representing a desired displacement of a synchro-transmitter shaft 2i, to which is attached a pointer 14 capable of indicating degrees of bearing on an associated dial i3, are programmed to be stored in selected magnetic cores in the matrix memory 11 of a digital computer. The organization of the computer corresponds to the programming technique which involves, in essence, the scheduling of the presentation of information signals to the computer data processing unit l2 on a time division basis by a programming unit 1t). Each step of the process represents a time interval, designated a word period, equal to that for any other step and is assigned a program count number (PC-tt). As shown in FlG. 2, an operation is performed by executing these steps in a predetermined sequence, said sequence including the repetition of steps or a subsequence of steps if required. Thus, during the word period designated as PCFl, the signals representing the desired bearing, i.e., the angular displacement of shaft 21 of indicating device 17 (FiG. l), are read out of memory l1, where they have been stored, and are set up in a register, the E register of data processing unit 12. The E register operates in synchronism with a second register, the F register, in which signals representing the present bearing, i.e., the present shaft displacement, are stored. ln PCi-.t2 the two registers are compared by comparator 23 and, if the number represented by the F register set of signals is the larger, a unit subtraction is made therefrom in PC#3 and then PCtt-tl is reentered; but, if the number represented by the E register set of signals is equal to or greater than the latter, a test for equality of the signals is made in PCi-*4. lf they are equal, no change is made in the content of the F register and PC1111 is reentered.; if they are unequal, it is an indication that the set of signals in the F register is the smaller and PC-S is entered. ln PC#5, a unit addition is made to the set of signals in the F register, and then PCi-rtl is reentered. A voltage pulse is transmitted to indicating device 17 by way of conductor 69 in correspondence with the unit addition to the F register made in PCi-5 or by way of conductor 68 in correspondence with the unit subtraction from the F register made in PC#3. Thus a unit alteration is made in the angular position of shaft 21, which change in position may be mechanically coupled by way of coupling 19 to a synchro-receiver 26 controlling the vehicle steering mechanism 2.7. The operations of the flow, i.e., the sequence from PC#1 to PC#2 to either PC#3 or PC#s 4 and 5, and from either PC-#3 or PC#5 back to PC4121, are repeated until the signals in the E and F registers are equal, at which time shaft pointer 14 will indicate the desired bearing. The operational sequence from PC#1 to PC#2 to PC#4 and back to PCail is now repeated until a new desired bearing is read out of memory 11 into the E register. It should be evident that the number of cycles of operation through one of the above paths'which cause alteration in the position of shaft 21 is equal to the initial difference, in the chosen units, between the present and desired indications and that each cycle provides a one unit addition or subtraction and one voltage pulse to indicating device 17. It is further evident that new numbers can be entered for indicating into the flow from memory 11 as rapidly as maneuvering conditions of the vehicle may warrant, since the time required for a computer excursion through the how is a small fraction of the time required for a maneuver condition to become evident.

The present computing system utilizes the magnetic core both for the storage of binary digits and in the logical circuitry. The magnetic core is used as a bistable state device and, for best results, the magnetic material, off which each core is composed, is distinguished preferably by having a rectangular major hysteresis characteristic, i.e., B-H curve, such as the one shown in FIG. 3a. The states of bistability prevail after core saturation, and are the two polari-ties of core remanent magnetization, here designated true and false, which will characterize the core indeiinitely if no further excitation is applied.

The excitat-ion, HM, required to drive a core from one state of saturation, eg., -BM, to the other, e.g., --BM, is critical, and the application of less than'this critical excitation, although causing nominal excursion, nevertheless does not essentially change the prevailing polarity of saturation. However, upon the application of excitation at least equal to 4the critical value in a direction to cause the core to take on a polarity of saturation opposite to that presently existing, the polarity of saturation will abruptly switch, as from the true state to the false state along the path of the descending arrow or from the false state to the true state along the path of the ascending arrow.

The present invention utilizes magnetic cores combined in a plurality of arrangements designated as registers To illustrate, FIG. 3 schematically shows the E register of data process-ing unit 12 (FIG. l) together with the lassociated equipment required to carry out the logical processes involved in the invention. This equipment is employed also in conjunction with the other registers to be described later. The E register contains two arrays of cores, one array 25, comprising storage cores E1s to E8s, inclusive, being employed for storage of the binary digits to be manipulated, and the other array 28, comprising control cores Elc to E4c, inclusive, being employed for purposes of performing the manipulation of these digits. The register also includes transfer circuit 22 which functions to delay the information read out from the arrays and sets -it up as an inhibiting signal capable of affecting the switching of cores in the E and other registers.

The utilization of magnetic cores as switching elements requires that they be driven from one state of remanent magnetization to the other by currents ilowing in windings inductively coupled to the core structure. Still referring to FIG. 3, the present system obtains drive for the cores from three generators; two generators 38 and 40, supply clock signals Cc and Cs on conductors 35 and 37, respectively, and one generator 39, supplies timing signals P1 to P8 on conductors 36. An additional period signal generator 16 is employed to produce a pair of signals W,3 and Ws, which are gated to transfer circuit 2 by way of or gate Ztl. All generators are connected to pulse source 15.

The combination of a clock signal Cc or Cs and each timing signal P1 to P8 defines eight digit transfer cycles of equal duration, during each of which one binary digit being stored in one of the cores E1s to ESS is made available for arithmetic manipulation. Due to the nature of the clock and timing signals, to be described later, each digit transfer cycle is divided into a sequence olf four.

equal time periods, designated as period Rs, period Wc, period Rc, and period WS. During period Rs the storage cores are interrogated, i.e., read out of; during period W the control cores are set, i.e., written into; during period RC the control cores are interrogated; and during period Ws the storage cores are set.

Still referring to FIG. 3, in the present system, each of the conductors, such as conductor 37 or conductor 41, supplying signals to the E register is connected to circuitry capable of generating a half-current of energy, i.e., half the excitation required to change the state of the core, or no excitation, i.e., zero current, at a particular time. Such conductors, which pass through and couple to a core with the same electrical sense so that currents therein are cumulative in their effect on the core polarity, are so indicated by diagonal marks across the cores in the same direction, such as diagonals 50 and 51 across core ESS. Such conductors which are poled oppositely to these are Iindicated by diagonal marks of opposite slope, such as diagonal 52 across core ESS.

Switching, therefore, can be accomplished by the coincident application of half-currents from two sources. As previously stated, these are a clock signal Cs or Cc, and a digital selector signal P1, P2, or P8. Further, core switching can be prevented by the application, coincident with the above, of a half-current from one of several other sources, e.g., an inhibiting signal from transfer circuit 22, or from other transfer circuits to be described later.

A core, if in the false state, will be switched to the true state by half-currents in the same direction, left to right in FIG. 3, 011 one of the conductors 36 and on conductor 35 or conductor 37. A core, if true, will be switched false by coincident half-currents from right to left on these conductors. If it is understood that currents from left to right are positive and those from right to left are negative, it may be seen that for core E1s, yfor instance, only a positive half-current on each of the conductors carrying signals P1 and Cs flowing simultaneously can switch the core to the true state, and conversely only a negative half-current on each of these conductors owlng simultaneously can switch the core to the false state. It will be further understood that when a core is to be interrogated, it is supplied with full negative current so that its resulting condition is the false state, and that when a core is to be set, it is supplied with an uninhibited full positive current so that its resulting condition is the true state. Thus it follows that a negative half-current emitted simultaneously from storage clock signal generator 40 and from digit selector signal generator 39 can interrogate storage cores while a positive half-current emitted simultaneously from these generators can set storage cores. Similarly, as will be shown subsequently, a negative halfcurrent emitted simultaneously from control clock signal generator 38 and from digit selector signal generator 39 can interrogate control cores while a positive halfcurrent emitted simultaneously from these generators can set control cores. Also, it may be observed that a double diagonal 95 is employed to symbolize that signal Cc is coupled twice through the control cores of the E register. This is to indicate that a half-current flowing in two loops of conductor 35 about each of these cores will suice to switch them. A core matrix may be arranged in this way when, in accordance with lits governing equation, a core is to be active during all digit transfer cycles making up the computer word. Conductors 41 and 42 connect outputs Es and Es of transfer circuit 22 to cores of the E register and, as will be shown, to the control cores of all other registers. Similarly, conductors labelled to correspond with outputs from other register transfer circuits, such as J', Ks', etc., serve to connect their transfer circuits to the E register. Conductor 47 is coupled to all cores of the E register and conveys a pulse type signal to transfer circuit 22 whenever a core of the E register changes in polarity of magnetization.

FIG. 3 further indicates that the signals generated by signal generators 38, 39, and 40 are all driven from a common pulse source 15. Pulse source may be a multivibrator or the like as are familiar to practitioners in the art. Additionally, it will be observed that or gate is supplied with signals Wc and Ws by period signal generator 16. Generator 16 comprises a network arranged to provide the pulse outputs shown in synchronism with periods Wc and WS. Or gate 20v is arranged to provide a logical or signal (Wc-t-Ws) for gating the input to transfer circuit 22 so as to pass pulses 0n conductor 47 received only as a result of the change of state of a core during an interrogation period. Generator 16 and or gate 2@ are also well known in the art and will not be further described.

FIGS. 7 through 1l show the details of the F, A, I, K, and L registers, respectively, of the computer. It will be noted that these registers, together with the E register of FG. 3, are operative to perform the system of the invention. Cores of the registers are threaded by similarly labelled conductors. 1t will be understood that all conductors similarly labelled are connected in series and are terminated so as to provide closed circuitry with respect to their respective sources.

Reference will next be made to FIG. 5 showing the overall combination of the E register of FIG. 3 with the F and A registers shown in FGS. 7 and 8, to provide the `data processing unit 12 utilized in the present invention. As noted, each of the E, F, and A registers is provided with a transfer circuit. in addition, the storage and control cores of each register are threaded with clock signals Cs and Cc, respectively, and timing signals P1 to P8 When appropriate. 1n addition, the outputs of the register transfer circuits, Es', ES, Fs', Fs, AS', and As, are made available for threading through the cores of their own and the other registers.

Data and control information input to data processing unit 12 is from memory 11 (FIG. l). Data information is received by way of output MS of a transfer circuit which is set up with data representing a new bearing as stored in memory 11. Control information, to indicate when the new bearing is to be set up in the E register, may originate in either memory 11 or at another source, and is received by way of outputs BS' and Bs, also preferably of a transfer circuit.

Output from data processing unit 12 is by way of two indicator drive cores 60 and 61, which are controlled to provide pulse outputs to drive indicating device 17.

FIG. 6 shows the l, K, and L registers comprising programming unit 1t? for data processing unit 12 of FG. 5. The cores of these registers are likewise each divided into storage and control cores and threadedwith clock signals Cs and CC, respectively, and timing signals P1 to P8 when appropriate. The transfer circuit outputs, ls', JS, Ks', Ks, LS', and LS, for these registers are threaded through the cores of their own and the other registers such that the outputs IS', JS, KS', K5, LS', Ls from programming unit t have impressed thereon during each word period (P1 through P8) a unique combination of signals. As noted these outputs are routed to the cores of data processing unit 12 and thread the control cores thereof, thereby rendering certain of them effective during each program count #2.

It should be further noted that the transfer circuit outputs of the E, F, and A registers of data processing unit 12 in FIG. 5 supply inputs to the cores of the programming unit 10 such that the advancement of this latter unit at the end of each word period is conditioned upon the results of operations by data processing unit 12 during the word period. The interaction of data processing unit 12 and programming unit 10 to provide for sequencing in accordance with the flow of FiG. 2 is exemplied by the graphs of transfer circuit outputs shown in FIG. 6a, which will be later discussed.

Referring now to FIG. 3b, here is shown the group of current waveforms, Cs, Cc, P1 to P8, which are generated synchronously and combined as shown for sequentially interrogating and setting cores through which the conductors carrying these signals are passed. Each is a square waveform of current having maximum values, such as at regions 54 and 55 of the signal Cs wave, equal to the positive or negative half-current. These maximum values, for each case, exist for a time period somewhat in excess of the switching time required by the core material, and the phasing of the currents is such that, depending upon whether a core is used for storage or for control, it is interrogated at a coincidence of negative half-current of signal CS or Cc with a negative half-current of signal P1, P2, or P8 during period RS or RC and is set at a coincidence of positive half-current of signal Cs or signal CC with a positive half-current of signai P1, P2, or P3 during period Ws or Wc.

'Ihe art is well versed in techniques for generating square wave signals of current such as signals CS, Cc, and P1 to P8, inclusive. It should therefore suffice to point out that each of these is a recurrent square waveshape with excursions of half-current amplitude, when present on their respective conductors. It should be noted that signal CC is identical to signal Cs, but is shifted two periods with respect thereto, and that each of these signals are at the zero current level for half of the digit transfer cycle. Further, it should be observed that signals P1, P2, and P8 appear successively on their respective conductors, but whichever is presently effective is synchronized with the generation of signals CS and Cc, as shown. Thus it follows that each of these P signals prevails only during every eighth digit transfer cycle, but is equally effective in establishing, by combining with Cs and Cc, the four iterative periods RS, Wc, RC, and Ws.

It has been pointed out in connection with PG. 3 that pulse voltages induced on sense conductor 47, as a result of change in core state, comprise the input to the E register transfer circuit 22.

The block diagram of the transfer circuit Z2 in HG. 4 shows that Voltage pulses carried by conductor 47 provide an input to amplifier 9S. The phase of each of these pulses is negative, owing to the direction of threading conductor 47 through the cores. Amplier 98 is gated to pass a signal on line 47 by a second input signal Wc-t-WS from or gate Zit (FlG. 3). This signal has the ability to cut off conduction in amplifier 93 during periods Wc and WS, and thus only signals on line 47 which occur during periods Rs and Re appear in ampliiied form as the true input to a flip-flop 96. 'fhe false input to iiip-op 96 is the negative-going pulse obtained by differentiating the logical sum square waveform Wc-i-Ws. Flip-flop 96 is constructed in accordance with the familiar arrangement which permits triggering from one of its bistable states to the other by only negative-going voltage pulses applied alternatively to a pair of inputs. The actual triggering to the false state occurs as a result of the negative pulse produced by the fall of the waveforms at the termination of every Wc and Ws period. Thus iiipiiop 96 may be triggered true during periods Rs and Rc as a result of a change in state of one of the E register cores; and, if so, this state will prevail until the end of periods Wc and Ws, respectively.

Flip-flop 96 is characterized by two outputs. One output, on line 66, is high only when the ip-ilop is in the true state and the other output, on line 74, is high only when the flip-Hop is in the false state. Both outputs are amplified without inversion by identical amplifiers, the former by amplifier 71 and the latter by amplifier 72. Amplifiers 71 and 72 have their inputs also gated by signal WC-i-Ws. However, due to the circuit arrangement of amplifiers 71 and 72, signals on lines 66 and 74, respectively, are passed only during periods Wc and Ws, and conduction is cut off during periods Rs and Rc. It should be noted that by this arrangement the signal read from the cores during an Rs and Rc period are effectively delayed and generated during the following Wc and Ws periods, respectively. The outputs of amplifiers 71 and 72, designated as outputs Es and Es', are of half coreswitching amplitude current z'/ 2. Conductors 41 and 42 pass through the register cores, being coupled to selected cores so that the delayed signals generated thereon may inhibit the setting of the cores during set periods Wc and WS, respectively.

FIG. 4a contains curves which further illustrate the operation of transfer circuit 22 for two representative digit transfer cycles. The successful interrogation of E register cores will be assumed during two successive interrogation periods Rc and Rs, resulting in -the shown negative pulses 80` and 82. Amplifier 98 is active during these periods and thus pulses 80 and 82 provide true triggering pulses 84 and 86, respectively, for flip-flop 96. However, at the fall of pulses Wc and Ws such as 87, 88, and 89, false triggering pulses are produced, such as pulses 90, 91, and 92, respectively, which reset ip-op 96 to the false state. Output on line 66 becomes high coincident with pulses 84 and 86 and becomes low coincident with pulses 91 and '92, and output on line 74 becomes low coincident with pulses 84 and 86 and high coincident with pulses 91 and 92, respectively. Since amplifiers 71 and 72 are cut off during interrogation periods, it is during period Ws of the first digit transfer cycle and period Wc of the second digit transfer cycle, that output Es on line 42 is high and output Es on line 41 is low. Thus, as a result of a change of state of an E register control core during period Rc of the first digit transfer cycle, for instance, an inhibiting signal half-current 93 (Es) is supplied at the output of the E register transfer circuit during the next period Ws; but where there is no change of state of an E register core, as during period Rc of the second digit transfer cycle, there is an inhibiting signal half-current 94 (Es) supplied at the output of the E register transfer circuit during the next period Ws. l

In the present system, handling of information in the storage cores of a register is serial, the information being arranged in a group consisting of a fixed number of binary digits. A group represents a number comprising eight binary digits and will be designated as a word A word consists of a sequence of eight binary digits; thus each of the E and F registers contains eight storage cores E1s to E8s and Fis to F8s, respectively, and each register may s-tore a number. The storage scheme employed herein utilizes the register core with the lowest numerical prefix, such as cores E1s, to store the least significant digit of a number and the other cores of a register to store the other digits of the number in order of greater significance, core ESS, for example, ybeing used to store the most significant -digit of the binary number in the E register. Digits are read into or read out of a register also in order of significance, being selected by the timing signals P1 to P8; signal P1 selects the digits in cores E1s and Fls, signal P2 selects the digits in cores E2s and F2s, ctc. Further, the time required for the sequence from signal P1 to signal P8 will be referred to as a word period. In summary, each word period is divided by the P signals into eight binary'periods, designated as digit transfer cycles, during each of which the condition of a core may be altered by the application of the P signal coincident with the application of signal Cs or Cc, in accordance withthe four sequential periods Rs, Wc, Rc, and Ws comprising each digit transfer cycle, as already described.

Referring now to the flow diagram, FIG. 2, in the preferred system, processes are performed sequentially, each process being definable within a word period. It is the function of programming unit 10 (FIG. 6) to render various of the con-trol cores operable during each word period in accordance with the logicalv equations defining the process. Accordingly, each output count signal, #1, #2, etc., of programming unit 10 indicates which of the control cores are operable during a word period.

The output count signals of programming unit 10 are composites of the read-out signals of pragramming storage cores Ils, K1s, and L1s, the states of which are determined by the control cores of the respective registers. The states of these control cores are, in turn, dependent on read-out signals of the cores of all registers, which signals cause the respective transfer circuits to generate inhibiting signals on conductors wound on these cores in accordance with the desired logical equations.

Table I shows the states of storage cores 11s, K1s, and Lls of programming unit 10 to produce each output count signal corresponding to the blocks in the fiow diagram of FIG. 2. With reference to terminology employed in this specification, it will be understood that a core in the true state (FIG. 3a) will be considered to be storing a binary digit one while a core in the false state will be considered to be storing a binary digit zero.

Table I ProgrammingT Unit Storage Cores Jrls K1s Lls Stages 2 0 2 1 2 2 Each configuration of cores J 1s, K1s, and L1s is maintained for one word period during which time the block functions, as expressed by the brief statements in the blocks and the equations thereunder, are being carried out. The output count signal from programming unit 10 is maintained for periods P1 through P8 of a word period (with the exception of the final period Ws of P8), and is subject to being changed at the end of the word period in accordance with the states of cores Ils, K1s, and Lls as evidenced during period Wc of P8 in order that the same or other control cores may become operable during the next word period.v In summary, from Table I, if, for example, during periods P1 through P8 of a word period, core K1s is true and cores Ils and Lls are false, the processes laid down in PC#2 of FIG. 2 are being performed. Depending on the outcome of these processes, core Als will be set true or permitted to remainA false. During period Ws of P8 of this Word period, cores 11s, K1s, and L1s will be reset depending upon the final state of core Als. Thus cores I 1s and K1s may be true and core Lls may be false (PC#3) or cores 11s and K1s may be false and core Lls may be true (PC#4) during periods P1 through P8 of the succeeding word period. To illustrate, with reference to FIG. 2, if, in PC#2., the F register number is greater than the E register number, cores Als and J 1s will be set true and cores K1s and L1s will remain as before (true and false, respectively), corresponding to PC#3. If, however, the E register number is equal to or greater than the F register number, cores Als and Ils will remain false and cores K1s and L1s will change state (to false and true, respectively), corresponding to PC#4.

Before going into the details of FIG. 2, it is appropriate to briefly review the operation of the registers in perform ing various logical processes, using the E register of FIG. 3 as illustrative.

With regard to storage cores E1s and ESS, it is seen that these may switch only at succeeding periods from period Pl (the core E1s digit transfer cycle) to P8 (the core ESS digit transfer cycle), and all are affected by inhibiting signal Es. Considering core Els as exemplary, it will be understood that all control cores Ele to E40 may affect the switching of core E1s; cores Ele and E2C during PC-#L core E during PCifs 2 and 3, and core Edic during PC#S 4 and 5. Core E30 is also affected by signal Es. Thus, still using the word period of PC#2 as illustrative, information set up in core E1s will 'oe read out at period Rs of digit transfer cycle P1, which, for simplicity, will be designated as period PlRS. The information will then be set up in core E30 at period PlWc, read out of core ESC at period PlRc, and reset in core Els at period PlWs. ln other words, information existing in core E1s will be restored in core E1s. If however, it were desired that information in core E1s be complemented during period P1, regardless of its initial state, it is only necessary that signal Es be coupled to core Els and that the opposite output, Es, of transfer circuit 22 be utilized as inhibiting signal for core E30. With this arrangement, regardless of the initial state of core E1s, its state at the end of period P1 will be the opposite, or, in other words, information in core Els is complemented. These and other logical processes are summarized in Table II.

Table II Inhibiting Signals With reference to the core designations, it will be understood that the true state of core E1s will be represented by a symbol such as E1s, and the signal or combination of signals which permits a core to be set to this state will be els; the false state of this core will be represented by a symbol such as E1s', and the signal which sets a core to this state will be gels. However, since the transfer circuit for a register is set up with data read from the storage cores Els, E25, etc., in turn, the outputs of the E register transfer circuit, ES and Es', generally represent data read from any of these cores.

It will be further understood that the computer contemplated here contains a core memory, read-in and readout techniques therefor being well established. It may thus be assumed that a signal Bs is provided (at the halfcurrent level) when a new indication on indicating device i7 (FIG. 5) is desired and read out from the memory, and a signal BS is provided as long as no new indication is desired. Similar to the other inhibiting signals which may affect core switching, signals Bs and BS may be the outputs of a transfer circuit, as shown.

Also, it will be understood that the process of reading information out of the core memory is arranged such that a memory core Mis changes state in correspondence with the information being read out. Therefore, if, for instance, the E register is to be filled from the memory, during a Pn digit transfer cycle, information read by interrogation of core Mis during period Rs is set up in an E register control core during period WC, is then read by interrogation of the control core during period Rc and,

finally, is set up in the Pn activated storage core during period Ws,

The details of FIG. 2 will next be referred to in explaining the operation of the system of the invention.

lt will first be recalled that, if a new number representing a desired indication of indicating device 17 (FIG. l) is not ordered to be read from memory 11, the sequence from PCtfl to PC#2 to PC#4 and back to PC#1 will be repeated continuously by the circuit of the present invention. However, if a new number is ordered to be read from memory if, the sequence from PC#1 to PC#2 to PC#3 to PC#1 or the sequence from PC#1 to PCi-Z to PC#4 to PC#5 to PC#l will be performed a number of times corresponding tothe difference between the present indication and the desired indication.

Referring specifically to PCii'l, this word period is distinguished by the fact that storage cores I 1s, Kls, and Lis of the J, K, and L registers, respectively, of programming unit 10 are characterized by the states shown in the first row in Table l', previously introduced, Thus, during this word period, cores Eic and E2C of the E register (FIG. 3) are not inhibited `from switching by signals from the registers of programming unit 10, whereas cores E30 and Elie are so inhibited. Since this type of core selection is used for program control, Table III accordingly lists the control cores of the E, F, and A registers (FIGS. 3, 7, and 8, respectively) in association with the PC# for which they are not inhibited.

Table III Control Cores Not inhibited E Register F Register' A Register Flc F20 lle, 120; ABC

Fic; F5c A4c F ao, Ao; A70 FGc; F7c A80 lt is the main function of PCitl to set up the E register storage cores Eis to E35 (FlG. 3) with the digits of a new bearing read out from memory il. As stated, this is done only if core Bis is true. Referring to FIG. 3, if core Bis is false, during period PlRS, no pulse will trigger the transfer circuit (FIG. 5) associated with core Bis and signal es will thus inhibit core El@ from switching during period PlWc; however, core E2C will not be so inhibited and thus will be set or not during period PIWC in accordance with the state of core E1s. The

activity of cores lZs to Eis during their respective digit transfer cycles is similar. Thus, if core Bls is false during the word period of PCitl, core E2C will effectuate the restoration of information in cores Els `to ESS. For example, if the symbol Es is employed to generically designate any of the cores Eis to ESS, and the symbol es is employed to designate the application of full switching current to any of these cores, and the symbols Es and ES' used to designate a true and false strate, respectively, of any of these cores, the equation for this activity is: es=BSES. On the other hand, if core Bis is true during period PlRs, there will be a pulse to the transfer circuit associated with core Els. lt follows that during period PlWc, signal Bs will inhibit core E2C from switching;

however', core Bie will not be so inhibited and thus will be set or not in accordance with the state of core Mis (FiG. 5), since the output Ms of the transfer Circuit associated with core Mis affects core Ele. Thus, if core Bls is true during the word period of PC#1, core Ele will cause the entry of the information of core Mls into cores Eis to ESS; the generic equation for this activity is written eszBSMS. in summary, the composite E register Boolean equation for PCitl is es=BsMS-|-BSES. It is noted from FIG. 3 that the first term BSMs of this equation is mechanized by core Elc While the second term BSEs of this equation is mechanized by core E2C as follows. The equation is seen to comprise the sum (logical or) of two product (logical and) terms and may Ibe logically manipulated to the equivalent expression Core Elc mechanizes the sum (Bs-MS) since the false outputs of the transfer circuits associated with cores Bls and Mls are inhibit wound to this core. Similarly, core E2C mechanizes the sum (Bs-l-Es') since the true output of the core Bls transfer circuit and the yfalse output of transfer circuit 22. are inhibit wound to this core. The primes of these sums are accomplished by the inhibit type of winding in which currents act to cancel the effect of current in the Cc signal winding 35, and the formation of the final sum is accomplished by common sense winding 47.

PC#1 further provides for restoration of the F register information, represented by the equation fs=Fs. This is required since, as will be recalled, the F register holds a number corresponding to the present setting of indicating device 17, `and this number must be retained for the comparison in PC#2.

The next statement made in PCttl directs that the registers of programming unit be arranged such that the processes of PC#2 be performed during the succeeding word period. It should be evident at this time that the equations J`S=JSP1 7, kS=KSP1 7, and l =LSP1 7 retain the arrangement 100 set up in cores Ils, Kls, and Lls during Ws of these periods to distinguish the word period of PC#1 shown in Table I. This is maintained for periods PlWs to PqWS, inclusive, by cores Ilc (FIG. 9), Klc (FIG. 10), and Llc (FIG. ll). Period PgWs is utilized to change to the 010 arrangement which distinguishes PC#2. It is thus necessary to switch core I ls false and core Kls true. Core I 1s is switched false at period PSWS, since no control core is provided for affecting core J 1s for this period (FIG. 9) and, as shown by Table II, this condition will cause the filling of a zero. A similar arrangement in the L register (FIG. 1l) permits core Lls to remain false. Core Kls is Set true at period PWS, since control core K2c is not inhibited at this time (FIG. 10), and this condition will cause the lling of a one.

The last statement of PC#1 indicates that core Als remains false. The A register (FIG. 8) will be later discussed. It will suffice at present to indicate that core Als enters and leaves the Word period of PC#1 in the false state.

During the word period of PC#2, the numbers in the E and F registers are compared and core Als is set to indicate the result of the comparison as follows. If the F register number is the greater, core Als is set true, otherwise it remains false. If core Als is true at period PsWS, the routine Will advance to PC4153 but if core Als is false at period PBWS, the routine will advance to PC#4.

In order that the comparison be made, the numbers in the E and F registers are made available by recirculation, represented by the equations es=Es, fs=Fs, the E register by core ESC (FIG. 3) and the F register by core F (FIG. 7) which, as shown in the PC-#Z row in Table III, are active during this word period.

The digits (states of cores Els to ESs and Fls to FSS) are compared, as these cores are interrogated, and reset during the corresponding P periods. It has been pointed out that core Als enters PC#2 in the false state. The scheme of the comparison is to set core Als true if an vE register storage core is storing a one and the corresponding F register core is storing a zero, and to set core Als false if the E register storage core is storing a zero and the corresponding F register storage core is storing a one; otherwise, core Als is not to be changed. This 1.2 comparison is given for all possible states of the E and F register storage cores and core Als in Table IV.

Table IV Core Als Core Coro Logic Es Fs Prior After aB and ai. to a P a P Period Period 0 0 0 0 EE'FBAB 0 0 l 1 EEFS* s 0 l 0 1 EsFr e 0 1 l l ESFBAS 1 O 0 0 EBFEAS' l 0 1 0 ESR/A5 l l 0 0 ESMAS l l l l EEFEAE Thus the equation determiningthe true state of core Als after a digit transfer cycle is:

aS=ESFsAS-l-EsFSAS'-1-ESFsA-i-EFAS which reduces, by logical manipulation, to

aS=ES^FS-l-ESAs-l-FSAs From Table III and FIG. 8, it is seen that control cores Alc, A2c, and A3c, respectively, accomplish the mechanization of the terms Vof the above equation, the

' common sense conductor 70 veffectively providing the logical sum of the terms.

With reference to output of programming unit 10, the information (Table I) in cores Jls, Kls, and Lls is recirculated during periods P1 to P7 in order to maintain the PC#2 count. If the comparison has indicated that (F) (E), it is desired that the next word period be PC#3; this condition requires only that core Ils be set true during period P8. However, if the comparison has indicated that (E)(F), it is desired that the next word period be PC#4; this condition requires that the states of cores Kls and Lls be complemented during period P8. In other words, the result of the comparison determines how the information in cores Ils, Kls, and Lls is to be changed during period P8. Since the condition determining a true state of cores J ls and Kls is the same as that determining the state of core Als, the same equation terms may be employed to represent the activity of cores Ils and Kls during period P8 as was employed for core Als, namely,

Core Lls, however, must remain false if (F (E) (i.e., if core Als is set true) and is set true if (E)(F) (i.e., if core Als remains false) and thus is governed during period P8 by terms of Table IV corresponding to a false state in core Als after a digit transfer cycle. From Table IV, the equation is therefore which reduces to: I :FsAs'-ESFSA-ESAS'.

It is noted that cores J2e, 13e, and I4c of FIG. 9 and cores KSC, K4c, and KSC of FIG. l0 are employed to form the respective terms of the is and ks equations while cores L20, L3c, and Llc` of FIG. l1 are employed to form the respective terms of the ls equation.

Referring to FIG. 6a, here are shown graphs of the waveshape outputs of the transfer circuits of programming unit 10 (FIG. 6) for the specific case of a sequence from PC#2 to PC#4. It is evident that recirculation of the PC#2 content (OlO) and the PC#4 content (001) of cores I ls, Kls, and Lls, respectively, occurs for periods P1 through P, of each word period. Further, dur- Table V Initial Status Final Status Logic of Cores of Cores Fs Als Fs Als f5 aE 0 O 0 0 1 l 1 Its/AE FBAB 1 0 1 (l FBAE l 1 0 (l From Table V it is noted that the equation specifying that an F register store core be set true is fszFslAs-FFSAS,

and the equation specifying that core Als be set true is :ISL-FS'AS. The terms of the former equation are developed by cores F4c and FSc of FlG. 7 While the term of the latter equation is developed by core A4c` of FIG. 8. The logic of PCil3 will effectuate a unit subtraction from the number in the F register. It is also necessary to generate a pulse signal to cause backward activation of indicating device 17 so that pointer 14 will read correctly. As shown in FIG. l2, this pulse is provided on conductor 63 by indicator drive core 60 during period PSWC when core 6l), which is normally false, is set true. The direction in which conductor 63 is wound through core 6&9 provides for a positive voltage pulse. This pulse is conducted through diode 66 and via conductor 68 to activator 18 of indicating device 17. Activator 18 has the ability to reposition shaft 21 counterclockwise in response to a pulse on conductor 68 or clockwise in response to a pulse on conductor 69. It should be noted that during period FSRc of PC#3, a negative pulse will appear on conductor 63 when core 66 is interrogated. It is the function of diode 66 to block this pulse from entering activator 1S. With regard to program control for PC#3, the Ils, Klis, and Lls equations (FIG. 2) indicate that the content of these cores is recirculated during periods P1 to P7. During period FsllJs, in order to change the output of programming unit l@ from 11G (Table I) to 100 (for FCX-i1), core 11s is set true by not inhibiting core JSC (Table Il and FIG. 9) and cores Kls and Lls are set false by not utilizing control cores during this period. Still with reference to FIG. 2, in the event the test made in PCitZ shows that (E)(F), core Als is set false and the output of programming unit 10 is set up for FC#4. During this word period, a further test is made to determine whether (E)=(F). If (E)=(F), core Als will be set false and the output of programming unit 10 will be arranged for PCtl once more, since it is not necessary to change the content of the F register. If, however, (15)#(11), this is an indication that the E register number exceeds that in the F register. When this condition prevails, core Als will be set true and the output of programming unit l0 Will be arranged for PC#5, which, as will be shown, provides for a unit being added to the content of the F register and a positive pulse being transmitted to activator 18 of indicating device 17 via conductor 59 (FIG. 12).

Regarding Table 1V again, then, and considering the states of the E and F register storage cores which combine with a true state of core Als or for which (E) 14 is not equal to (F), the equation governing a true state of core Als may be Written:

which reduces to: aS=AS+ESFS-{-ESFS.

Referring to FIG. 8, it is noted that cores ASC, A66, and A7c mechanize the respective terms of this equation.

Program control for PC#4 requires that the G01 content (Table I) of cores 11s, KIs, and L1s be recirculated during periods P1 to P7. If PCiiS is to be set up for the next word period, as shown by a final true state of core Als, core `11s must be set true, core L1s must remain true, and core Kls remains false. lf, however, PCitl is to be set up for the next word period, as shown by a final false state of core Als, the content of cores Ils and Lls must be complemented and core Kls remains false. Thus, during period P8 cores Ils and Lis are governed by the same equation as core Als. Referring to FIGS. 9 and 1l, it is seen that cores JSC, 16e, and J7c of the former and cores L50, Lec, and L70 of the latter mechanize this equation. Core Kls is set false since no control core is provided in the K register (FIG. 10) for period P8 of PCtM.

Considering now the word period of PC#5, it is required that a unit be here added to the number stored in the F register; core Als is utilized in the addition. Table VI may be referred to in order to develop the equations representing the addition.

From Table VI it is noted that the equation specifying that an F register storage core be set true is fs=FsrAs+FsAsi and the equation specifying that core Als be set true is ISIFSS The terms of the former equation are developed by cores F6c and F7C of FIG. 7 while the term of the latter equation is developed by core ASC of FIG. 8.

The logic of PC#5 will effectuate a unit addition to the number in the F register. It is also necessary to generate a pulse signal to cause fom/ard activation of indicating device 17 so that pointer 14 will read correctly. As shown in FIG. l2, this pulse is provided on conductor 64 by indicator drive core 61 in the same fashion as discussed for the activity of core 60 during PC#3.

With regard to program control for PC#5, the Ils, I ls, and Lis equations (FIG. 2) indicate that the content of these cores is recirculated during periods P1 to F7. During period PSWS, in order to change the output of programming unit 10 from lOl (TABLE I) to 100 (for PC#1), core Jls is set true by not inhibiting core 39C (Table Il and FIG. 9) and cores Kls and L1s are set false by not utilizing control cores during this period.

Still referring to FIG. 2, an example of the operation of the system of the present invention will next be given. It will be presumed that initially the E register content is 53 and that previous sequences through the flow of FIG. 2 have occurred a sufficient number of times so E register cores... E88 E78 E63 E5s E43 E38 E2s E1s F register cores F83 F78 F68 Fs F4s FBS F2s F13 Binary order 27 2 25 24 23 22 2l 20 Content (53) 0 0 1 1 0 1 0 1 The flow now occurring is'from PC#1 to P-C#2 to PC#4 and back to PC#1 as follows. Starting in PC-#L presuming that it is not now desired to change the bearing or other indication represented by the number 53, core 131s is false. Thus the E and F register contents are recirculated and PC#2 is entered. Here the registers are compared and the number in the F register is found to be not larger than that in the E register. Core Als remains false asl a result of the comparison and PC#4 is entered. The equality test in PC#4 is successful, core Als continues in the false state and PC#1 is re-entered. indicating device 17 is not pulsed and the indication thereof, 53, is not changed.

It is now desired that the indication be changed to 143. This number is entered into the computer memory 11 (FiG. 1) and core Bls is set true. At the next excursion of the flow through PCat'rl, the true state of core Bis will effectuate the replacementof the number 53 in the E register with the new bearing 143, expressed binarily as 10001111. In PC#2, the comparison will show that (E)(F), core Als will remain false and the routine will advance to PCi-t4. Here the test for equality will fail and core Alsv will be set true. In PC#5, a unit will be added to the F register content, which will become 54, expressed binarily as 00110110. Indicator drive core 61 (FIG. 12) will be set true and then false, and a pulse on conductor 64 will activate indicating device 17 to increase its indication by one unit. PC-#l will be re-entered. The sequence from PC#l'to PC#2 to PC#4 to PC#5 and back to PC#1 again-normally would be conducted 90 times until the F register attains the E register content, 143.

However, it will be further presumed that, when the F register attains a content of 97, expressed binarily as 01100001, a second new Abearing is entered into memory 11. This second bearing is 24, expressed binarily as 00011000. This number is entered into the E register during PC1121 and it is noted that it is less than the nurnber 97 presently in the F register. During PC#2, then, the comparison indicates that (F) (E), core 1As is set true and PC#3 is entered. Here a unit is subtracted from the F register content, which will become 96, expressed binarily as 01100000. Indicator drive core 60 (FIG. 12) will be set true and then false and a pulse on conductor 63 will activate indicating device 17 to decrease its indicati-on by one unit. PC#1 will be reentered. The sequence from PCql to PC#2 to PC#3 and back to PC#1 is repeated 73 times until the F register attains the E register content 24. Thus the reading for the pointer 14 of the indicating devicey 17 agrees with the desired bearing and the circuitry merely re- Icirculates without providing any further control pulses until a new bearing is read into the E register yfrom the memory.

While the Iform of the invention' shown `and described herein is admirably adapted to fulfill the objects primarily stated, it is to be understood that it is not intended to confine the invention tot the one form or embodiment disclosed herein, for it is susceptible of embodiment in various other forms, and the invention is therefore to be limited only as indicated by the scope of the appended claims.

What is claimed is:

l. A digital computer for performing logical operations on stored data on successive word periods, the combination comprising: iirst Ameans including means for providing signal demarking computer operating intervals; a data processing unit for performing the operations, vsaid data processing unit including a plurality of inhibit- Wound magnetic core registers; a programming unit for controlling the operations to be performed by said data processing unit, said programming unit also including a plurality of inhibit-wound magnetic core registers, each said register for both said units comprising a respective array of storage cores for storing data, a respective array of control cores for performing logical arithmetical 0perations on stored data, and a respective common sense conductor for both said arrays, and transfer circuit means connected to and responsive to signals generated on said sense conductor, for supplying inhibiting signals to the cores of the registers, said transfer circuit means being constructed and arranged to receive respective signals gener-ated on their sense conductors during one operating interval and in response thereto produce corresponding contemporaneous inhibit signals during the next succeeding operating interval, and including means to apply at least two of the produced inhibit signals to respective inhibit windings of at'least one of the register cores; means connected to said rst means, including a source of timing signals for defining a computer word period and a Vsource of storage and control clock signals, the signals from saidsources providing composite four phase read-write driving signals for both the storage and control cores of said registers, each saidtransfer circuit means being operable to supply its respective inhibiting signals coincident with the'write driving signals `for one of the arrays in accordance with data signals read out of the other of the arrays, and said transfer circuit means for said programming unit also operable to supply inhibiting signals coincident with the Write driving signal to render certain of the control cores of said data processing unit registers operable.

2. A cyclically operable digital computer operable through time intervals each termed a computer word period, said computer comprising a data processing unit anda programming unit, each of which comprises a plurality of registers each of which registers includes first and second magnetic core arrays; a source of read signals and write signals Afor the several first arrays, and a source-oi read signals and write signals for the severalsecond arrays; for each of said registers, a respective commonv sense conductor for the pair of `arrays thereof; and for each of said registers a respective means comprising a transfer circuit responsive to signals on its respective sense conductor-for supplying inhibiting signals to the cores of at least one of the registers; said iirst and second magnetic core arrays in Ia register comprising respectively a set of storage cores and a set of control cores, the control cores of a register of said data processing unit being operative to perform a logical arithmetic operation on a datum from an associated storage core in accordance lwith inhibiting signals obtained from storage cores of said data processing unit in response to registers -by -a read signal within a computer word period; and the transfer circuits of said programming unit registers providing inhibiting signals to the control cores of said data processing unit to render certain of said control cores eiective during each word period.

3. A cyclically operable digital computer operable through time intervals each termed a computer word period, said computer comprising a data processing unit and a programming unit, each of which comprises a plurality of registers each including respective storage and control magnetic core arrays; means including respective sources of recurring read signals `and write signals for the storage and the control arrays; for each register a respective common sense conductor for the arrays and a transfer circuit responsive to signals provided on the sense conductor as a result of switching cores by a read signal, said transfer circuit supplying inhibiting signals to cores of at least `two of the registers during the application thereto of a write signal; each of the control 

